UW-FLASHR

Abstract

Time-based medium access control (MAC) has potential advantages over FDMA and CDMA approaches in terms of hardware simplicity, energy efficiency, and delay. Unfortunately, the channel utilization of existing TDMA and CSMA acoustic MAC protocols is generally low due to the long propagation delays of acoustic signals. In this work, we argue that several ideas taken from RF protocols, including exclusive channel access, are either unnecessary in acoustic networks or must be redefined. We present and evaluate UW-FLASHR, a time-based MAC protocol which does not require centralized control, tight clock synchronization, or accurate propagation delay estimation. We demonstrate that UW-FLASHR can achieve significantly higher channel utilization than the maximum utilization possible with existing time-based exclusive access MAC protocols, particularly when the ratio of propagation delay to transmission delay is high or data payloads are small.